DE 20 2011 005 058 describes a transformer with a switching device. This transformer comprises a three-phase primary winding, a three-phase first secondary winding and a three-phase second secondary winding with tap adjustment. Each secondary winding has a group of three individual windings. Provided in this context are three independent switching means, by which the groups of individual windings of the first and the second secondary winding are connectable in different ways.
Due to the numerous contacts, such switching means have a complex and elaborate structure so that it presents a great challenge to put them into service properly. Furthermore, it is not only costly, but also complicated to control and operate the respective switching means separately. In addition, the installation of individual switching means takes up a particularly large amount of space in the individual transformers, making them to large for regular transport.
A switching assembly for switching one of at least three windings during transformer operation to at least one of three main windings of a phase of the transformer is known as “Advanced Retard Switch”, abbreviated as ARS, from the patent applier company brochure under the title of “Advanced-Retard-Switch (ARS), Betriebsanleitung BA 274/01”, imprint BA 274/0lde, 0605, published in June 2005, and is schematically illustrated in FIG. 13. At least one subassembly is provided for each phase to be switched. Arranged in each subassembly are fixed contacts for each phase to be switched. The fixed contacts are selectively switchable in each subassembly by one movable switch contact each, each of which switch contacts is fastened on a switching mechanism. This switching assembly can be used for different applications in combination with an on-load tap changer. The switching assembly is primarily used for reversing the polarity of the regulating voltage in applications with wide regulating ranges, such as phase-shifting transformers, for example. It then functions as a double reversing change-over selector.
DE 1 788 013 [U.S. Pat. No. 3,590,175] describes a tap selector for a tapped transformer with an additional change-over selector for increasing the number of possible voltage steps. In this context, the movable change-over selector contacts are each arranged in segments around the tap selector column in a support frame. By the segmented design, they can each produce a connection between a middle change-over selector contact and selectively one of two further change-over selector contacts. The support frame used here consists of a plurality of vertical insulation rods and upper and lower lever arms. This known arrangement relates to a change-over selector on a tap selector, however not to a switching assembly of the type previously mentioned and referred to as “Advanced Retard Switch”.
DE 1 249 990 describes a star-point rotary off-circuit tap-changer for multi-phase tapped transformers where the fixed contacts are arranged circularly around a central off-circuit tap-changer shaft in a plurality of horizontal levels assigned to the individual phases of the transformer. This off-circuit tap-changer shaft holds the movable contacts that consist of U-shaped flat brackets that each in turn electrically conductively connect two adjacent fixed contacts. This star-point rotary off-circuit tap-changer, which serves for load-free change-over switching between winding taps, is not suited as “Advanced Retard Switch”.
DE 10 2007 023 124 [U.S. Pat. No. 8,030,583] describes a switching assembly with two operating positions for change-over switching of a winding during transformer operation, where the through-current is commutated from one current path to another current path when change-over switching is carried out. In this context, fixed contacts are arranged in a plurality of horizontal levels around a rotatable switching shaft on a structure of insulation material. These contacts have upper and lower contact fingers that can be pulled apart and are switchable by an electrically conductive rail serving as movable switch contact.